Combination of spark plug and combustion chamber having connected conical and cylindrical sections

ABSTRACT

A spark plug for use in a rotary engine, having an outer electrode projected from the lower end surface of the metal shell of the spark plug along and spaced apart from an inverted conical surface of an ignition opening of the rotary engine to locate a spark discharge gap near a combustion chamber.

United States Patent 1111 3,597,648

721 Inventors Masao Shibagaki 511 Int. (:1 .1101: 13/54, Asa-gun: H01113/20, F02b 53/00 lkuo Ogasawara, Nagoya, both of, Japan [50] Field ofSearch 313/143 [2i] Appl. No 686,166 [22] Filed Nov. 28, 1967 ReferencesCited 45 Patented Aug. 3, 1971 UNITED STATES PATENTS 1 Assignees 102,238,852 4/1941 Regar 313 143 x AH'GIIII; 2,391,456 12/1945 Hensel313/143 x NGK Spark Plug 2,586,864 2/1952 Rose 313/143 x ti ne 2,591,7184/1952 Paul 313/143 x 1 1 Priority 099-1, 1966 2,616,407 11/1952 Thomas313/143 x 1 J p (31 1 41/109731 Przmary Exammer- Robert Segal 3Attorney-Waters, Roditi, Schwartz & Nissen [54] COMBINATION OF SPARKPLUG AND ABSTRACT: A spark plug for use in a rotary engine, havingggfiggg an outer electrode projected from the lower end surface of the 2Cl s 3 D "in 5 metal shell of the spark plug along and spaced apart froman n g inverted conical surface of an ignition opening of the rotary[52] [LS-Cl 313/143, engine to locate a spark discharge gap near acombustion 313/141, l23/8.49, 123/809 chamber.

PATENTEI] Am; 3 Ian COMDINATION OF SPARK PLUG AND COMBUSTION CHAMBERHAVING CONNECTED CONICAL AND CYLINDRICAL SECTIONS The present inventionrelates to a spark plug for use in a retary engine.

The spark plug of the rotary engine is detachably mounted in theinnermost part of an ignition opening of the rotary engine from theoutside. This'ignition opening is circular in secdischarge gap G.

tion and formed in that part of a casing of the rotary engine whichserves to compress and ignite a mixed gas by means of a rotor, saidcasing constituting a combustion chamber therein for the rotary engine.

The ignition opening is designed so that its diameter is made as smallas possible so as to prevent a draft of the mixed gas from occurringowing to the pressure difference between adjacent combustion chambersdivided by the rotor and that that part of the ignition opening whichsurrounds the spark discharge electrodes of the spark plug is formed asan inverted conical-shaped funnel for the purpose of facilitating asupply of the mixed gas to the spark gap and also of improvingmachinability of the ignition opening.

It is desired to locate the spark discharge electrodes as near thecombustion chamber as possible so as to improve the thermal property ofthe spark plug.

In the heretofore known spark plug an outer electrode is mounted on thelower end surface of the metal shell of the spark plug in parallel witha center axis of the shell or perpendicular to the lower end surface ofthe shell and the free end of the outer electrode is bent atsubstantially 90 in opposition to a center electrode so as to fonn aspark discharge gap therebetween. This construction causes the bentportion of the outer electrode to make contact with the conical surfaceformed at the innermost part of the ignition opening. Thus, it isimpossible to locate the spark discharge gap as near thecombustionchamber as possible and hence a satisfactory thermal propertyof the ignition plug could not be obtained.

The principal object of the invention, therefore, is to provide animproved spark plug for use in a rotary engine, which is particularlyadapted to locate its spark discharge gap as near the combustion chamberas possible and hence to obtain a satisfactorythermal property.

For a better understanding of the invention, reference is made to theaccompanying drawing, in which FIG. 1 is a front view of a spark plugpartially broken away for use in a rotary engine according to theinvention;

FIG. 2 is a longitudinal sectional view of essential parts of theelements of FIG. 1; and

FIG. 3 is a longitudinal sectional view of an rotary engine showing thespark plug according to the invention in the mounted state. I

Referring to the drawing, 1 designates a metal shell of a spark plug; 2a ceramic insulator housed in the shell; 3 a center electrode extendingthrough the ceramic insulator 2 and provided at its upper end with aterminal 3a; 4 an outer In accordance with the invention, the outerelectrode 4 is mounted at the lower end of the shell 1 so that the outerelectrode 4 is projected from the lower end surface 10 of the shell 1along and spaced apart from an inverted conical surface 5 formed at theupper end of an ignition opening 6 of the rotary engine, the ignitionopening 6 being formed in a casing 7 of the rotary engine and incommunication with a combustion chamber 8 in which a rotor 9 isrotatably mounted.

As explained hereinbefore, the spark plug for use in the rotary engineaccording to the invention and comprising the outer electrode mounted onthe shell so that the outer electrode is projected along and spacedapart from the conical surface forming the upper end of the ignitionopening of the rotary engine so as to minimize the distance from thelower end of the outer electrode to the combustion chamber ensureslocation of the outer electrode as closely adjacent to the upper conicalsurface of the ignition opening as possible without requiring anytroublesome operation and further provides the important advantage thatthe spark discharge gap is closely located near the combustion chamberand hence improves the thermal property of the spark plug.

Though the invention is described by means of an embodimentas shown inthe drawing, yet various modifications can of course be made withoutdeparting from the scope of the claim.

What we claim is:

I. For a rotary engine, the combination of a casing having an ignitionopening extending to a combustion chamber which is formed in the casing,and a spark plug in said ignition opening, said spark plug including ashell detachably mounted in said ignition opening and having a lowerend, an insulated center electrode mounted in said shell, and an outerelectrode mounted at said lower end of the shell and projecting intospaced relation with said center electrode to form a spark discharge gaptherewith, said ignition opening having a conical surface which narrowsin a direction away from said lower end and towards said combustionchamber, said ignition opening having a cylindrical portion extendingfrom said conical surface into said combustion chamber in substantialaxial alignment with said center electrode said lower end of the shellbeing of slightly reduced diameter compared to the remainder of theshell to form a space with said casing which extends into the ignitionopening at said conical surface said outer electrode including a portionextending from said lower end substantially parallel to said conicalsurface in closely spaced relation therewith, the latter portionprojecting towards said center electrode.

2. The combination as claimed in claim 1 wherein said outer electrodeincludes a bent portion extending perpendicular to the axis of saidcenter electrode from the first said portion beneath and iritoopposition to the lower end face of said center electrode.

1. For a rotary engine, the combination of a casing having an ignitionopening extending to a combustion chamber which is formed in the casing,and a spark plug in said ignition opening, said spark plug including ashell detachably mounted in said ignition opening and having a lowerend, an insulated center electrode mounted in said shell, and an outerelectrode mounted at said lower end of the shell and projecting intospaced relation with said center electrode to form a spark discharge gaptherewith, said ignition opening having a conical surface which narrowsin a direction away from said lower end and towards said combustionchamber, said ignition opening having a cylindrical portion extendingfrom said conical surface into said combustion chamber in substantialaxial alignment with said center electrode said lower end of the shellbeing of slightly reduced diameter compared to the remainder of theshell to form a space with said casing which extends into the ignitionopening at said conical surface said outer electrode including a portionextending from said lower end substantially parallel to said conicalsurface in closely spaced relation therewith, the latter portionprojecting towards said center electrode.
 2. The combination as claimedin claim 1 wherein said outer electrode includes a bent portionextending perpendicular to the axis of said center electrode from thefirst said portion beneath and into opposition to the lower end face ofsaid center electrode.